Apparatus and method for supplying plating solution to plating tank,  plating  system, powder container, and plating method

ABSTRACT

An improved apparatus for adding powder comprising at least a metal, such as copper, to a plating solution, and supplying the plating solution to a plating tank is disclosed. The apparatus includes a hopper having an inlet which is connectable to a powder conduit of a powder container holding the powder therein, a feeder which communicates with a bottom opening of the hopper, a motor coupled to the feeder, and a plating-solution tank coupled to an outlet of the feeder and configured to dissolve the powder in the plating solution.

CROSS REFERENCE TO RELATED APPLICATIONS

This document claims priorities to Japanese Patent Application Number 2016-023224 filed Feb. 10, 2016 and Japanese Patent Application Number 2016-220952 filed Nov. 11, 2016, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present invention relates to an apparatus and a method for supplying a plating solution to a plating tank. The present invention also relates to a plating system having such an apparatus. The present invention also relates to a powder container for holding metal powder to be used in plating. Further, the present invention relates to a method of plating a substrate using a plating solution to which metal powder for use in plating has been added.

As electronics are becoming smaller in size, higher speed, and less power consumption, interconnect patterns in a semiconductor device are becoming finer and finer. With the progress toward finer interconnect patterns, materials used for interconnects are changing from conventional aluminum and aluminum alloys to copper and copper alloys. The resistivity of copper is 1.67 μΩcm, which is about 37% lower than the resistivity (2.65μΩcm) of aluminum. Therefore, compared to aluminum interconnects, copper interconnects can not only reduce power consumption, but can also be made finer with the same interconnect resistance. In addition, because of the lower resistance, copper interconnects have the advantage of reduced signal delay.

Filling of copper into trenches is generally performed by electroplating which can form a film faster than PVC or CVD. In the electroplating, a voltage is applied between a substrate and an anode in the presence of a plating solution to deposit a copper film on a low-resistance seed layer (or a feeding layer) which has been formed in advance on the substrate. Such a seed layer is generally comprised of a thin copper film (copper seed layer) formed by, for example, PVD. Since there is a demand for a thinner seed layer with the progress toward finer interconnects, the thickness of the seed layer, which is generally of the order of 50 nm, is expected to decrease to not more than 10 nm to 20 nm in the future.

The applicant has proposed a plating apparatus that uses a plurality of concentrically-divided separate anodes which are individually connected to a plating power source (see Japanese Patent Laid-Open Publication No. 2002-129383). According to this plating apparatus, a current density of a centrally-located separate anode is made higher than an outer separate anode for a certain period of time when an initial plating film is formed on a substrate, thereby preventing a plating current from concentrating in the peripheral portion of the substrate, and allowing the plating current to flow also in the central portion of the substrate. This makes it possible to form a plating film having a uniform thickness even when a sheet resistance is high. The applicant has also proposed a plating technique that uses an insoluble anode (see Japanese Patent Laid-Open Publication No. 2005-213610 and Japanese Patent Laid-Open Publication No. 2008-150631). An anode holder for holding the insoluble anode is provided with a plating-solution discharge section for sucking and discharging a plating solution out of an anode chamber, and is also provided with a plating-solution injection section connected to a plating-solution supply pipe extending from a plating-solution supply apparatus.

In order to meet the recent demand for a smaller circuit system using semiconductors, implementation of semiconductor circuits in a package having approximately the same size as a chip has come into practical use. A packaging method called wafer level package (WLP) has been proposed as a method to perform implementation of semiconductor circuits in such a package. The wafer level package is generally classified into fan-in technique (also called WLCSP (Wafer-Level Chip-Scale Package)) and fan-out technique. The fan-in WLP is a technique for providing external electrodes (external terminals) in a chip-size area. The fan-out WLP, on the other hand, is a technique for providing external terminals in an area larger than a chip, for example, forming a re-distribution layer and external electrodes on a substrate formed of an insulating resin in which a plurality of chips are embedded. An electroplating technique is sometimes used for forming a re-distribution layer, an insulating layer, etc. on a wafer, and is expected to be applied also in the fan-out WLP. A higher level of technique, especially in control of a plating solution, is required in order to apply the electroplating technique in the fan-out WLP or the like for which finer pitches are strongly required.

With a view to performing so-called bottom-up plating, the applicant has proposed a method of plating a substrate, such as a wafer, while preventing a generation of an electrolyte component which inhibits bottom-up plating (see Japanese Patent Laid-Open Publication No. 2016-074975). This method involves bringing an insoluble anode and a substrate into contact with a copper sulfate plating solution containing additives, and applying a predetermined plating voltage from a plating power source to between the substrate and the insoluble anode to plate the substrate.

On the other hand, in order to replenish a plating solution with objective metal ions in a plating apparatus which uses an insoluble anode as described above, it is conceivable to use a method in which a powdery metal salt is fed into a circulation tank or a method in which metal pieces are dissolved in a separate tank for replenishment. When the powdery metal salt is supplied into a plating solution, fine particles increases in the plating solution and may cause a defect in a surface of a plated substrate. In view of this, the applicant has proposed a technique which can keep concentrations of components of a plating solution constant over a long period of time in a plating apparatus that uses an insoluble anode (see Japanese Patent Laid-Open Publication No. 2007-051362). This technique, which involves circulating and reusing a plating solution while recovering the plating solution, can minimize the amount of the plating solution used. Further, the use of an insoluble anode can eliminate the need for replacement of the anode, thereby facilitating maintenance and management of the anode. Furthermore, the concentration of a component(s) of the plating solution, which changes with the circulation and reuse of the plating solution, can be maintained within a certain range by supplying a replenishing solution, containing the plating solution component(s) at a concentration high than the plating solution, to the plating solution.

When plating of a substrate with copper is performed using an insoluble anode, copper ions in a plating solution decrease gradually. It is therefore necessary for a plating-solution supply apparatus to adjust the copper ion concentration in the plating solution. One possible method to replenish the plating solution with copper is to add copper oxide powder to the plating solution. However, if the powder scatters in a semiconductor manufacturing plant, it will cause pollution of a clean room. Further, the plating-solution supply apparatus is required to add a necessary amount of copper oxide powder to the plating solution without decreasing the throughput. In addition, there is an increasing demand for a plating technique which can form a higher-quality copper film on a substrate with use of such a plating solution to which copper oxide has been added.

SUMMARY OF THE INVENTION

In one embodiment, there is provided an improved apparatus and method for adding powder comprising at least a metal, such as copper, to a plating solution, and supplying the plating solution to a plating tank. In one embodiment, there is provided a plating system including such an apparatus. In one embodiment, there is provided a powder container for holding therein powder comprising at least a metal, such as copper, to be used in the above-described apparatus. In one embodiment, there is provided a plating method which can form a higher-quality metal film on a substrate with use of a plating solution to which powder comprising at least a metal, such as copper, has been added.

According to an embodiment, there is provided an apparatus for supplying a plating solution, in which powder comprising at least a metal to be used in plating has been dissolved, to a plating tank, comprising: a hopper having an inlet which is connectable to a powder conduit of a powder container holding the powder therein; a feeder which communicates with a bottom opening of the hopper; a motor coupled to the feeder; and a plating-solution tank coupled to an outlet of the feeder and configured to dissolve the powder in the plating solution.

In an embodiment, the apparatus further comprises: a weight measuring device configured to measure a weight of the hopper and the feeder; and an operation controller configured to control an operation of the motor based on a change in a measured value of the weight.

In an embodiment, the operation controller is configured to calculate an amount of the powder added to the plating solution from a change in the measured value of the weight, and instruct the motor to operate until the amount of the added powder reaches a target value.

In an embodiment, the inlet of the hopper has a connecting seal whose inner diameter gradually decreases with a distance from a distal end of the inlet.

In an embodiment, the connecting seal is composed of an elastic material.

In an embodiment, the apparatus further comprises an airtight chamber in which the inlet of the hopper is located, the airtight chamber including a door which allows the powder container to be carried into the airtight chamber, and a glove which constitutes part of a wall of the airtight chamber.

In an embodiment, the airtight chamber further includes an exhaust port for connecting an interior space to a negative-pressure source.

In an embodiment, a vibrating device capable of vibrating the powder container is disposed in the airtight chamber.

In an embodiment, a vacuum clamp capable of holding the powder container is disposed in the airtight chamber.

In an embodiment, the plating-solution tank includes an agitation device for agitating the plating solution.

In an embodiment, the plating-solution tank includes an agitation tank in which the agitation device is disposed, and an overflow tank coupled to a through-hole formed in a lower portion of the agitation tank.

In an embodiment, the plating-solution tank further includes a detour passage located adjacent to the overflow tank.

In an embodiment, the plating-solution tank further includes a plurality of baffle plates disposed in the overflow tank, the plurality of baffle plates being staggered.

In an embodiment, the apparatus further comprises: an enclosure cover that surrounds connection portions of the feeder and the plating-solution tank; and an inert-gas supply line which communicates with an interior of the enclosure cover.

According to one embodiment, there is provided a plating system comprising: a plurality of plating tanks each for plating a substrate; a plating-solution supply apparatus including (i) a hopper having an inlet which is connectable to a powder conduit of a powder container holding therein powder comprising at least a metal to be used in plating of the substrate, (ii) a feeder which communicates with a bottom opening of the hopper, (iv) a motor coupled to the feeder, and (v) a plating-solution tank coupled to an outlet of the feeder and configured to dissolve the powder in a plating solution; and a plating-solution supply pipe extending from the plating-solution supply apparatus to the plating tanks.

In an embodiment, the plating system further comprises a plating-solution return pipe extending from the plating tanks to the plating-solution supply apparatus.

According to one embodiment, there is provided a method of supplying powder, comprising at least a metal to be used in plating, to a plating solution, comprising: coupling a powder conduit of a powder container, holding the powder therein, to an inlet of a hopper; supplying the powder from the powder container to the hopper; operating a feeder which communicates with a bottom opening of the hopper while measuring a weight of the feeder and the hopper in which the powder is stored; and adding the powder to the plating solution by the feeder based on a change in a measured value of the weight.

In an embodiment, the method further comprises agitating the plating solution to which the powder has been added.

In an embodiment, the method further comprises: calculating an amount of the powder added to the plating solution from a change in the measured value of the weight; and operating the feeder until the amount of the added powder reaches a target value.

According to one embodiment, there is provided a powder container for holding powder comprising at least a metal to be used in plating, comprising: a container body capable of holding the powder therein; a powder conduit coupled to the container body; and a valve attached to the powder conduit.

In an embodiment, a distal end of the powder conduit has a shape of a truncated cone.

According to one embodiment, there is provided a method of plating a substrate, comprising: delivering a plating solution from a plating tank to a plating-solution tank; calculating an amount of powder to be added to the plating solution held in the plating-solution tank based on a metal ion concentration in the plating solution in the plating tank, the powder comprising at least a metal to be used in plating; supplying the powder to the plating solution held in the plating-solution tank; dissolving the powder in the plating solution held in the plating-solution tank; supplying the plating solution, in which the powder has been dissolved, from the plating-solution tank to the plating tank; bringing a substrate into contact with the plating solution held in the plating tank; and causing an electrochemical reaction in the plating solution held in the plating tank to deposit the metal on a surface of the substrate.

In an embodiment, the plating tank comprises a plurality of plating tanks, and wherein the plating solution is supplied from the plating-solution tank to each of the plating tanks while controlling a flow rate of the plating solution.

In an embodiment, the plating tank comprises a plurality of plating tanks, and a metal ion concentration in the plating solution in the plurality of plating tanks is continually monitored; and when the metal ion concentration has become lower than a predetermined value, the plating solution in the plating tanks is delivered to the plating-solution tank, while the plating solution in the plating-solution tank is supplied to one of the plurality of plating tanks.

According to one embodiment, there is provided a non-transitory computer-readable storage medium that stores a computer program for performing a method of electroplating a substrate, the method comprising: delivering a plating solution from a plating tank to a plating-solution tank; supplying powder to the plating solution held in the plating-solution tank, the powder comprising at least a metal to be used in plating; dissolving the powder in the plating solution held in the plating-solution tank; supplying the plating solution, in which the powder has been dissolved, from the plating-solution tank to the plating tank; bringing a substrate into contact with the plating solution held in the plating tank; and causing an electrochemical reaction in the plating solution held in the plating tank to deposit the metal on a surface of the substrate.

According to one embodiment, there is provided a non-transitory computer-readable storage medium that stores a computer program for performing a method of electroplating a substrate, the method comprising: monitoring whether a concentration of metal ions contained in a plating solution in a plating tank is lower than a predetermined value; calculating an amount of powder to be added to the plating solution when the concentration of metal ions is lower than the predetermined value, the powder comprising at least a metal; delivering the plating solution from the plating tank to a plating-solution tank; supplying the powder to the plating solution held in the plating-solution tank until an amount of the added powder reaches the calculated amount; dissolving the powder in the plating solution held in the plating-solution tank; supplying the plating solution, in which the powder has been dissolved, from the plating-solution tank to the plating tank; bringing a substrate into contact with the plating solution held in the plating tank; and causing an electrochemical reaction in the plating solution held in the plating tank to deposit the metal on a surface of the substrate.

The above-described embodiments can provide an apparatus and a method which can add the powder to a plating solution and dissolve the powder in the plating solution while preventing scattering of the powder. Further, according to the above-described embodiments, a high-quality metal film (e.g. copper film) can be formed on a substrate using a plating solution to which powder comprising at least a metal, such as copper, has been added.

The powder container, the plating system, and the plating method described above can be used also when a substrate is to be plated with a metal species such as indium, nickel, cobalt, or ruthenium, other than copper. Examples of powders usable in such a case may include: sulfates such as indium sulfate, nickel sulfate and cobalt sulfate; sulfamates such as nickel sulfamate and cobalt sulfamate; halides such as nickel bromide, nickel chloride and cobalt chloride; and indium oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic overall view of a plating system according to a first embodiment;

FIG. 2 is a side view of a powder container capable of holding copper oxide powder therein;

FIG. 3 is a view showing the powder container with a cap off and a valve open;

FIG. 4 is a perspective view of an airtight chamber;

FIG. 5 is a view showing the interior of the airtight chamber;

FIG. 6 is a view showing a distal end of a powder conduit of the powder container and an inlet of a hopper;

FIG. 7 is a view showing the distal end of the powder conduit of the powder container and the inlet of the hopper when they are in tight contact with each other;

FIG. 8 is a flow chart showing processes of supplying copper oxide powder from the powder container to the hopper;

FIG. 9 is a side view showing the hopper and a feeder;

FIG. 10 is a perspective view of a plating-solution tank;

FIG. 11 is a plan view of the plating-solution tank;

FIG. 12 is a vertical cross-sectional view of the plating-solution tank as viewed in a direction of arrow A shown in FIG. 11;

FIG. 13 is a schematic view of another embodiment of a plating-solution tank;

FIG. 14 is a schematic view of yet another embodiment of a plating-solution tank;

FIG. 15 is a diagram showing results of an experiment which was conducted to examine the influence of the number of baffle plates on dissolution of copper oxide powder;

FIG. 16 is a schematic overall view of a plating system according to a second embodiment;

FIG. 17 is a flow chart showing a control sequence for adding copper oxide powder to a plating solution in the plating system according to the first embodiment; and

FIG. 18 is a flow chart showing a control sequence for adding copper oxide powder to a plating solution in the plating system according to the second embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments will now be described with reference to the drawings. FIG. 1 is a schematic overall view of a plating system according to a first embodiment. The plating system includes a plating apparatus 1 installed in a clean room, and a plating-solution supply apparatus 20 installed in a downstairs room. In this embodiment, the plating apparatus 1 is an electroplating unit for electroplating a substrate (e.g., a wafer) with copper, and the plating-solution supply apparatus 20 is a plating-solution supply unit for supplying powder, comprising at least copper, into a plating solution to be used in the plating apparatus 1. In this embodiment, copper oxide powder is used as the powder comprising at least copper, while it is also possible to use pelletized materials comprising at least copper. In this embodiment, an average particle size of the copper oxide powder is in the range of 10 micrometers to 200 micrometers, more preferably in the range of 15 micrometers to 50 micrometers. If the average particle size is too small, the powder is likely to scatter as dust. On the other hand, if the average particle size is too large, the solubility of the powder, when fed into a plating solution, may be poor.

In this specification, the term “powder” or “particles” herein encompasses solid particles, shaped granular materials, pelletized solid materials, small-diameter solid copper balls, a strip-shaped material obtained by shaping solid copper into a ribbon-like or tape-like shape, or a combination thereof.

The plating apparatus 1 has four plating tanks 2. Each plating tank 2 includes an inner tank 5 and an outer tank 6. An insoluble anode 8, held by an anode holder 9, is disposed in the inner tank 5. Further, in the plating tank 2, a neutral membrane (not shown) is disposed around the insoluble anode 8. The inner tank 5 is filled with a plating solution, which is allowed to overflow the inner tank 5 into the outer tank 6. The inner tank 5 is also provided with a agitation paddle (not shown) comprised of a rectangular plate-like member having a constant thickness of 3 mm to 5 mm, made of a resin such as PVC, PP or PTFE, or a metal, such as stainless steel or titanium, coated with a fluororesin or the like. The agitation paddle reciprocates parallel to a substrate W to agitate the plating solution, so that sufficient copper ions and additives can be supplied uniformly to a surface of the substrate W.

The substrate W, such as a wafer, is held by a substrate holder 11 and is immersed, together with the substrate holder 11, in the plating solution held in the inner tank 5 of the plating tank 2. The substrate W, as an object to be plated, may be a semiconductor substrate, a printed circuit board, etc. In the case of using a semiconductor substrate as the substrate W, the semiconductor substrate is flat or substantially flat (a substrate having a groove(s), a tube(s), a resist pattern(s), etc. is herein regarded as substantially flat). When plating such a flat object, it is necessary to control a plating condition over time in consideration of the in-plane uniformity of a plating film formed on the substrate, while preventing a deterioration in the quality of the film.

The insoluble anode 8 is electrically connected via the anode holder 9 to a positive pole of a plating power source 15, while the substrate W held by the substrate holder 11 is electrically connected via the substrate holder 11 to a negative pole of the plating power source 15. When a voltage is applied from the plating power source 15 between the insoluble anode 8 and the substrate W that are both immersed in the plating solution, an electrochemical reaction occurs in the plating solution held in the plating tank 2, whereby copper is deposited on the surface of the substrate W. In this manner, the surface of the substrate W is plated with copper. The plating apparatus 1 may have less than four or more than four plating tanks 2.

The plating apparatus 1 includes a plating controller 17 for controlling the plating process of the substrate W. The plating controller 17 has a function of calculating a concentration of copper ions contained in the plating solution in each plating tank 2 from a cumulative value of electric current that has flowed in the substrate W. Copper in the plating solution is consumed as the substrate W is plated. The consumption of copper is proportional to the cumulative value of electric current that has flowed in the substrate W. The plating controller 17 can therefore calculate the copper ion concentration in the plating solution in each plating tank 2 from the cumulative value of electric current.

The plating-solution supply apparatus 20 includes an airtight chamber 24 into which a powder container 21, holding copper oxide powder therein, is to be carried, a hopper 27 for storing the copper oxide powder supplied from the powder container 21, a feeder 30 which communicates with a bottom opening of the hopper 27, a motor 31 coupled to the feeder 30, a plating-solution tank 35 coupled to an outlet of the feeder 30 and configured to dissolve the copper oxide powder in a plating solution, and an operation controller 32 for controlling the operation of the motor 31. The feeder 30 is actuated by the motor 31. An acidic copper sulfate plating solution containing sulfuric acid, copper sulfate, halogen ions, and organic additives, in particular a plating accelerator e.g. comprising SPS (bis(3-sulfopropyl) disulfide), a suppressor e.g. comprising PEG (polyethylene glycol) and a leveler e.g. comprising PEI (polyethylenimine), may be used as the plating solution. Chloride ions are preferably used as the halogen ions.

The plating apparatus 1 and the plating-solution supply apparatus 20 are coupled to each other by a plating-solution supply pipe 36 and a plating-solution return pipe 37. More specifically, the plating-solution supply pipe 36 extends from the plating-solution tank 35 to a bottom of the inner tank 5 of each plating tank 2. The plating-solution supply pipe 36 is divided into four branch pipes 36 a, which are coupled to the bottoms of the inner tanks 5 of the four plating tanks 2, respectively. The four branch pipes 36 a are provided with respective flow meters 38 and respective flow control valves 39. The flow meters 38 and the flow control valves 39 are coupled to the plating controller 17. The plating controller 17 is configured to control a degree of opening of each flow control valve 39 based on a flow rate of the plating solution measured by the flow meter 38. Therefore, the flow rates of the plating solutions supplied to the plating tanks 2 through the four branch pipes 36 a are regulated by the flow control valves 39, provided upstream of the plating tanks 2, so that the flow rates are kept substantially the same. The plating-solution return pipe 37 extends from the bottom of the outer tank 6 of each plating tank 2 to the plating-solution tank 35. The plating-solution return pipe 37 has four discharge pipes 37 a coupled to the bottoms of the outer tanks 6 of the four plating tanks 2, respectively.

The plating-solution supply pipe 36 is provided with a pump 40 for delivering the plating solution, and a filter 41 disposed downstream of the pump 40. The plating solution that was been used in the plating apparatus 1 is delivered through the plating-solution return pipe 37 to the plating-solution supply apparatus 20. The plating solution to which the copper oxide powder has been added in the plating-solution supply apparatus 20 is fed through the plating-solution supply pipe 36 to the plating apparatus 1. The pump 40 may continually circulate the plating solution between the plating apparatus 1 and the plating-solution supply apparatus 20, or may intermittently deliver a predetermined amount of the plating solution from the plating apparatus 1 to the plating-solution supply apparatus 20, and may intermittently return the plating solution, to which the copper oxide powder has been added, from the plating-solution supply apparatus 20 to the plating apparatus 1.

In order to replenish the plating solution with pure water (DIW), a pure-water supply line 42 is coupled to the plating-solution tank 35. This pure-water supply line 42 is provided with an on-off valve 43 (which is usually open) for stopping the supply of pure water when the operation of the plating apparatus 1 is stopped, a flow meter 44 for measuring a flow rate of the pure water, and a flow control valve 47 for controlling a flow rate of the pure water. The flow meter 44 and the flow control valve 47 are coupled to the plating controller 17. The plating controller 17 is configured to control a degree of opening of the flow control valve 47 to supply the pure water into the plating-solution tank 35 in order to dilute the plating solution when the copper ion concentration in the plating solution has exceeded a set value.

The plating controller 17 is coupled to the operation controller 32 of the plating-solution supply apparatus 20. The plating controller 17 is configured to send a signal indicating a replenishment demand value to the operation controller 32 of the plating-solution supply apparatus 20 when the copper ion concentration in the plating solution has become lower than a set value. Upon receipt of the signal, the plating-solution supply apparatus 20 adds the copper oxide powder to the plating solution until the amount of the added copper oxide powder reaches the replenishment demand value. Although in this embodiment the plating controller 17 and the operation controller 32 are constructed as separate devices, in one embodiment the plating controller 17 and the operation controller 32 may be constructed as one controller. In that case, the controller may be a computer that operates in accordance with a program. The program may be stored in a storage medium.

The plating apparatus 1 may include concentration measuring devices 18 a each for measuring the copper ion concentration in the plating solution. The concentration measuring devices 18 a are attached to the four discharge pipes 37 a of the plating-solution return pipe 37, respectively. A measured value of the copper ion concentration obtained by each concentration measuring device 18 a is sent to the plating controller 17. The plating controller 17 may compare the above-described set value with a copper ion concentration in the plating solution calculated from the cumulative value of electric current as discussed previously, or may compare the above-described set value with a copper ion concentration measured by the concentration measuring device(s) 18 a. The plating controller 17 may correct the calculated value of the copper ion concentration based on a comparison of a copper ion concentration in the plating solution, calculated from the cumulative value of electric current (i.e., calculated value of the copper ion concentration), with a copper ion concentration measured by the concentration measuring device(s) 18 a (i.e. measured value of the copper ion concentration). For example, the plating controller 17 may determine a correction factor by dividing a measured value of the copper ion concentration by a calculated value of the copper ion concentration, and correct a calculated value of the copper ion concentration by multiplying the calculated value by the correction factor. The correction factor may preferably be updated periodically.

The plating-solution supply pipe 36 may have a branch pipe 36 b, which is provided with a concentration measuring device 18 b to monitor the copper ion concentration in the plating solution. The branch pipe 36 b may be further provided with an analyzer(s) (e.g. a CVS device or a colorimeter) to perform quantitative analysis and monitoring of the concentration of a dissolved chemical component(s) in addition to the copper ion. Such a construction makes it possible to analyze the concentration of the chemical component, e.g. an impurity, in the plating solution existing in the plating-solution supply pipe 36 before the plating solution is supplied to the plating tanks 2. This can prevent the dissolved impurity from affecting the plating performance and can more ensure highly-precise plating. Only one of the concentration measuring devices 18 a, 18 b may be provided.

With the above-described construction, the plating system according to the first embodiment can replenish the plating solution with copper while keeping the copper ion concentration in the plating solution substantially equal among the plating tanks 2.

FIG. 2 is a side view of the powder container 21 capable of holding copper oxide powder therein. As shown in FIG. 2, the powder container 21 includes a container body 45 capable of holding copper oxide powder therein, a powder conduit 46 coupled to the container body 45, and a valve 48 attached to the powder conduit 46. The container body 45 is composed of a synthetic resin, such as polyethylene. The container body 45 has a handle 49 so that a worker can grip the handle 49 to carry the powder container 21. While there is no particular limitation on the volume of the powder container 21, the volume should be such that a worker can carry the powder container 21 filled with the copper oxide powder. In one example, the volume of the powder container 21 is 4 L. Not only non-shaped copper oxide powder but pellets (granules) that have been shaped from copper oxide powder can also be used as copper oxide to be filled into the powder container 21. The use of the pelletized copper oxide powder can more effectively prevent scattering of dust.

The powder conduit 46 has been joined to the container body 45 by a joining technique, such as welding. The powder conduit 46 is comprised of a pipe that allows the copper oxide powder to pass therethrough. The powder conduit 46 is inclined at an angle of about 30 degrees with respect to the vertical direction. The copper oxide powder can pass through the powder conduit 46 when the valve 48, mounted to the powder conduit 46, is open, while the copper oxide powder cannot pass through the powder conduit 46 when the valve 48 is closed. FIG. 2 shows the powder conduit 46 with the valve 48 closed. A cap (or lid) 50 is attached to a distal end 46 a of the powder conduit 46.

FIG. 3 is a view showing the powder container 21 with the cap 50 off and the valve 48 open. The copper oxide powder is fed through the powder conduit 46 into the powder container 21 in the state shown in FIG. 3. After the completion of feeding of the copper oxide powder, the valve 48 is closed, and the cap 50 is mounted on the distal end 46 a of the powder conduit 46 (see FIG. 2). The powder container 21 with the valve 48 closed, filled with the copper oxide powder, is carried into the airtight chamber 24 shown in FIG. 1.

FIG. 4 is a perspective view of the airtight chamber 24. In this embodiment, the airtight chamber 24 is a rectangular box capable of forming a hermetically-space therein. The airtight chamber 24 includes a door 55 which allows the powder container 21 to be carried into the interior space of the airtight chamber 24, and two gloves 56 which constitute part of a wall of the airtight chamber 24. A mount frame on which the door 55 is mounted is comprised of a member having a sealing function, such as a rubber, so that the interior of the airtight chamber 24 can be hermetically sealed. Each of the gloves 56 is comprised of a membrane formed by a flexible material (e.g. synthetic rubber, such as polyvinyl chloride) which can deform so as to follow a shape of a worker's hand, and is configured to be able to project into the airtight chamber 24 so that a worker can conduct operations inside the airtight chamber 24. The two gloves 56 are located at both sides of the door 55. The airtight chamber 24 has an exhaust port 58 for connecting the interior space of the airtight chamber 24 to a negative-pressure source. The negative-pressure source is, for example, a vacuum pump. A negative pressure is created in the airtight chamber 24 through the exhaust port 58.

FIG. 5 is a view showing the interior of the airtight chamber 24. In the airtight chamber 24 are disposed a vacuum clamp 61 for holding the powder container 21 by vacuum suction, a vibrating device 65 for vibrating the powder container 21, and a pedestal 66 for supporting the powder container 21. The powder container 21, with its powder conduit 46 facing downward, is set on the vacuum clamp 61 and the pedestal 66. The vacuum clamp 61 is secured to a frame 68, and the vibrating device 65 is secured to the vacuum clamp 61. The vacuum clamp 61 has a vibration-proof rubber 61 a which is to make contact with the powder container 21. The vibration-proof rubber 61 a has a through-hole (not shown) in which a vacuum is to be created. The operations of the vibrating device 65 and the vacuum clamp 61 are controlled by the operation controller 32 shown in FIG. 1.

The vacuum clamp 61 is coupled to an ejector 70 which is a vacuum creating device. The ejector 70 and the vibrating device 65 are coupled to a compressed-air supply pipe 72. The compressed-air supply pipe 72 is divided into two pipes; one is coupled to the ejector 70, and the other is coupled to the vibrating device 65. When compressed air is fed into the ejector 70, the ejector 70 creates a vacuum in the vacuum clamp 61, so that the powder container 21 can be held on the vibration-proof rubber 61 a of the vacuum clamp 61 by vacuum suction. The vibrating device 65 is configured to operate by the compressed air. The vibrating device 65 transmits the vibration to the powder container 21 through the vacuum clamp 61, thereby vibrating the powder container 21 held by the vacuum clamp 61. A frequency of vibration of the vibrating device 65 is controlled by a vibration controller (not shown) of the plating-solution supply apparatus 20. The vibration controller may be comprised of the operation controller 32. The vibrating device 65 may directly contact the side surface of the powder container 21. In an embodiment, the vibrating device 65 may be an electric vibrating device.

An inlet 26 of the hopper 27, which is connectable to the powder container 21, is located in the airtight chamber 24. The distal end 46 a (see FIG. 3) of the powder conduit 46 of the powder container 21 is inserted into the inlet 26 of the hopper 27 (see FIGS. 6 and 7), whereby the distal end 46 a of the powder conduit 46 of the powder container 21 is coupled to the inlet 26 of the hopper 27. When the valve 48 is opened after the powder conduit 46 and the inlet 26 are coupled (see FIG. 7), the copper oxide powder in the powder container 21 flows through the powder conduit 46 into the inlet 26, and finally falls into the hopper 27.

A bridge phenomenon of copper oxide powder may occur in the powder container 21 in the vicinity of the powder conduit 46. The bridge phenomenon is a phenomenon in which the powder container 21 is clogged with the copper oxide powder due to an increase in the density of the powder. In order to prevent such bridge phenomenon, the vibrating device 65 vibrates the powder container 21, thereby fluidizing the copper oxide powder in the powder container 21. The frequency of the vibration of the vibrating device 65 may be in the range of 1000 to 10000 per minute, more preferably 7000 to 8000 per minute.

The powder conduit 46 is fixed at such a position on the powder container 21 that the entirety of the powder container 21, with its powder conduit 46 coupled to the inlet 26 of the hopper 27, is inclined. In particular, when the powder conduit 46 is connected to the inlet 26 of the hopper 27, one side of the powder container 21 is inclined at an angle of 50 to 70 degrees with respect to a horizontal plane, while other side is inclined at an angle of 20 to 40 degrees with respect to the horizontal plane. In this manner, when the powder conduit 46 is coupled to the inlet 26 of the hopper 27, the right and left sides of the powder container 21 are inclined toward the powder conduit 46 at different angles. Accordingly, the pressure of powder, which concentrates in the vicinity of the powder conduit 46, differs between the right and left sides of the powder conduit 46, thereby effectively preventing the occurrence of the bridge phenomenon. Consequently, the copper oxide powder can be quickly discharged and, in addition, is unlikely to remain in the powder container 21.

FIG. 6 is a view showing the distal end 46 a of the powder conduit 46 of the powder container 21 and the inlet 26 of the hopper 27. The distal end 46 a of the powder conduit 46 has a shape of a truncated cone. The inlet 26 of the hopper 27 has a shape corresponding to the shape of the distal end 46 a of the powder conduit 46. More specifically, the inlet 26 of the hopper 27 has a connecting seal 28 whose inner diameter gradually decreases with a distance from a distal end (upper end) of the inlet 26. The connecting seal 28 is composed of an elastic material, such as rubber. As shown in FIG. 7, when the distal end 46 a of the powder conduit 46 is inserted into the inlet 26 of the hopper 27, the distal end 46 a of the powder conduit 46 comes into tight contact with the connecting seal 28 of the inlet 26, so that a gap between the distal end 46 a of the powder conduit 46 and the inlet 26 of the hopper 27 is sealed by the connecting seal 28. Scattering of the copper oxide powder can therefore be prevented.

The operation of supplying the copper oxide powder from the powder container 21 to the hopper 27 will now be described with reference to FIG. 8. In step 1, the powder container 21, filled with the copper oxide powder, is prepared. In step 2, the door 55 of the airtight chamber 24 is opened, and in step 3, the powder container 21 is carried into the airtight chamber 24. The door 55 is closed in step 4 and, in step 5, a worker wears the gloves 56 and takes off the cap 50 of the powder container 21 in the airtight chamber 24. In step 6, the powder conduit 46 of the powder container 21 is coupled to the inlet 26 of the hopper 27, and in step 7, the valve 48 of the powder container 21 is opened, and in step 8 the powder container 21 is vibrated by the vibrating device 65 while the powder container 21 is held on the vacuum clamp 61. The copper oxide powder in the powder container 21 is supplied through the inlet 26 into the hopper 27. Upon completion of the feeding of the copper oxide powder, the vibration of the powder container 21 is stopped in step 9, the valve 48 is closed in step 10, and the vacuum suction of the powder container 21 by the vacuum clamp 61 is stopped in step 11. In step 12, the powder container 21 is removed from the vacuum clamp 61 and the pedestal 66, and in step 13 the cap 50 is attached to the powder conduit 46. In step 14, the door 55 is opened, and in step 15 the powder container 21 is taken out of the airtight chamber 24.

All the above steps 1 to 15 are performed while a negative pressure is produced in the interior of the airtight chamber 24. The powder container 21 is in the airtight chamber 24 from when the valve 48 is opened to when the valve 48 is closed. Therefore, even if the copper oxide powder spills from the powder container 21, the copper oxide powder does not leak from the airtight chamber 24. A volume of the hopper 27 is several times larger than the volume of the powder container 21; therefore, the above steps 1 to 15 are repeated until a sufficient amount of copper oxide powder is stored in the hopper 27.

The hopper 27 and the feeder 30 will now be described. FIG. 9 is a side view showing the hopper 27 and the feeder 30. The hopper 27 is a powder reservoir (or pellet reservoir) in which copper oxide powder supplied from the powder container 21 is to be stored. A lower half of the hopper 27 has a shape of a truncated cone so that the copper oxide powder can flow downward smoothly. A top opening of the hopper 27 is covered with a lid 74. The inlet 26, which is to be coupled to the powder conduit 46 of the powder container 21, is secured to the lid 74. Further, an exhaust pipe 75 is secured to the lid 74. This exhaust pipe 75 communicates with the interior space of the hopper 27, and further communicates with a not-shown negative-pressure source. Therefore, a negative pressure is created in the interior space of the hopper 27 through the exhaust pipe 75.

The feeder 30 communicates with the bottom opening of the hopper 27. In this embodiment, the feeder 30 is a screw feeder having a screw 30 a. The motor 31 is coupled to the feeder 3, so that the feeder 30 is actuated by the motor 31. The hopper 27 and the feeder 30 are secured to a bracket 73. This bracket 73 is supported by a weight measuring device 80. The weight measuring device 80 is configured to measure the total weight of the hopper 27, the feeder 30, the motor 31, and the copper oxide powder present in the hopper 27 and the feeder 30.

The outlet 30 b of the feeder 30 is coupled to the plating-solution tank 35. When the motor 31 actuates the feeder 30, the copper oxide powder in the hopper 27 is fed by the feeder 30 into the plating-solution tank 35. An enclosure cover 81, which surrounds connection portions of the feeder 30 and the plating-solution tank 35, is secured to the plating-solution tank 35. The outlet 30 b of the feeder 30 is located inside the enclosure cover 81. An inert-gas supply line 83 is coupled to the enclosure cover 81, and communicates with the interior of the enclosure cover 81. The inert-gas supply line 83 supplies an inert gas, such as nitrogen gas, into the enclosure cover 81 to fill the interior of the enclosure cover 81 with the inert gas.

The inert gas is supplied into the enclosure cover 81 for the following reason. The plating-solution tank 35 may be operated such that the plating solution in the plating-solution tank 35 is maintained at a high temperature. In such a case, a vapor generates from the plating solution. The vapor rises and reaches the connection portions of the feeder 30 and the plating-solution tank 35, and intrudes through the outlet 30 b into the feeder 30. When the vapor is adsorbed onto the copper oxide powder existing in the feeder 30, the copper oxide powder can agglomerate and may clog the feeder 30. In order to avoid this, the inert gas, such as nitrogen gas, is injected into the enclosure cover 81 so as to expel the vapor downward, thereby preventing the vapor from intruding into the feeder 30.

The weight measuring device 80 is coupled to the operation controller 32, which controls the operation of the motor 31. A measured value of the weight outputted from the weight measuring device 80 is sent to the operation controller 32. The operation controller 32 receives the signal indicating the replenishment demand value that has sent from the plating apparatus 1 (see FIG. 1), and instructs the motor 31 to operate until an amount of the copper oxide powder, which has been added to the plating solution in the plating-solution tank 35, reaches the replenishment demand value, while calculating the amount of the added copper oxide powder from a change in the measured value of the weight outputted from the weight measuring device 80. The motor 31 actuates the feeder 30, which adds the copper oxide powder, in the amount corresponding to the replenishment demand value, to the plating solution in the plating-solution tank 35. The replenishment demand value is a value that varies depending on the copper ion concentration in the plating solution so as to reflect the consumption of copper ions in the plating solution held in the plating tanks 2. The replenishment demand value is a target value of an amount of copper oxide powder to be added to the plating solution held in the plating-solution tank 35.

The plating controller 17 is configured to calculate the replenishment demand value from the copper ion concentration in the plating solution in the plating tanks 2 when the copper ion concentration in the plating solution in the plating tanks 2 has become lower than a set value. As described above, the copper ion concentration in the plating solution in the plating tanks 2 may be the copper ion concentration calculated from the cumulative value of the electric current, or the copper ion concentration measured by the concentration measuring device(s) 18 a and/or the concentration measuring device 18 b.

If a large amount of copper oxide powder is added to the plating solution in a short time, the copper oxide powder may agglomerate before it is dissolved in the plating solution, and as a result, the copper oxide powder may not be fully dissolved. Moreover, if a rotational speed of the screw 30 a of the feeder 30 is too high, the copper oxide powder may agglomerate in the feeder 30 and may form lumps which are hardly soluble in the plating solution. In order to prevent the formation of such agglomerates and lumps of the copper oxide powder, it is preferred to set an upper limit of the rotational speed of the screw 30 a. More specifically, the operation controller 32 preferably controls the motor 31 so that the screw 30 a rotates at a rotational speed not more than the preset upper limit.

The operation controller 32 may preferably issue an alarm when an amount of copper oxide powder stored in the hopper 27 has become small. More specifically, the operation controller 32 may preferably issue an alarm when the measured value of the weight outputted from the weight measuring device 80 has become lower than a lower limit.

The plating-solution tank 35 will now be described. FIG. 10 is a perspective view of the plating-solution tank 35, FIG. 11 is a plan view of the plating-solution tank 35, and FIG. 12 is a vertical cross-sectional view of the plating-solution tank 35 as viewed in a direction of arrow A shown in FIG. 11. The plating-solution tank 35 includes an agitation tank 91 in which an agitation device 85 is disposed, and an overflow tank 92 coupled to a through-hole 95 formed in a lower portion of the agitation tank 91. The overflow tank 92 communicates with the agitation tank 91 through the through-hole 95. The plating-solution return pipe 37, which is coupled to the plating tanks 2 as shown in FIG. 1, is coupled to the agitation tank 91. Thus, the plating solution used in the plating apparatus 1 of FIG. 1 is returned to the agitation tank 91.

The outlet 30 b of the feeder 30 is located above the agitation tank 91, and the copper oxide powder is fed from the feeder 30 into the agitation tank 91. The agitation device 85 includes agitating blades 86 disposed in the agitation tank 91, and a motor 87 coupled to the agitating blades 86. The copper oxide powder can be dissolved in the plating solution by the agitating blades 86 which are rotated by the motor 87. The operation of the agitation device 85 is controlled by the operation controller 32. The overflow tank 92 is located adjacent to the agitation tank 91. The plating solution to which the copper oxide powder has been added flows from the agitation tank 91 into the overflow tank 92 through the through-hole 95. The through-hole 95 may be provided with a filter to prevent passage of undissolved copper oxide powder.

A detour passage 93 is provided adjacent to the overflow tank 92. The plating solution overflows the overflow tank 92 into the detour passage 93. The detour passage 93 in this embodiment is a tortuous or meandering passage formed by a plurality of baffle plates 88. Each baffle plate 88 has a cutout portion 88 a formed in one end. The cutout portions 88 a of two adjacent baffle plates 88 are located at different positions with respect to a longitudinal direction of the baffle plates 88. Accordingly, as illustrated by arrows in FIG. 11, the flow of the plating solution to which the copper oxide powder has been added meanders through the detour passage 93. In one embodiment, the detour passage 93 may be formed by a plurality of baffle plates 88 which are staggered and have no cutout portions 88 a.

The detour passage 93 is provided in order to ensure a sufficient time for the copper oxide powder to be dissolved in the plating solution. The time required for the plating solution to pass through the detour passage 93 is preferably not less than 10 seconds. Such detour passage 93 enables the copper oxide powder to be fully dissolved in the plating solution.

FIG. 13 is a schematic view of another embodiment of the plating-solution tank 35. In this embodiment, baffle plates 88 are installed in the overflow tank 92, and are staggered in the vertical direction. A detour passage 93 for the plating solution is formed by these baffle plates 88.

FIG. 14 is a schematic view of yet another embodiment of the plating-solution tank 35. In this embodiment, an agitation tank 91 in which an agitation device 85 is disposed is installed in the center of the plating-solution tank 35. An overflow tank 92 is disposed outside the agitation tank 91 and communicates with a through-hole 95 formed in the lower end of the agitation tank 91. A detour passage 93 is provided adjacent to the overflow tank 92 and is coupled to the plating-solution supply pipe 36. The detour passage 93 is located outside the agitation tank 91 and the overflow tank 92. In this embodiment, the detour passage 93 is a spiral passage that extends spirally. The plating solution flows from the agitation tank 91 into the overflow tank 92 through the through-hole 95, and overflows the overflow tank 92 into the detour passage 93. The plating solution that has flowed through the detour passage 93 flows into the plating-solution supply pipe 36. The detour passage 93 in a spiral shape, i.e., in a circular shape, enables the plating solution to stay for a long time in the plating-solution tank 35 without use of the baffle plates 88. Further, there is no corner in the plating-solution tank 35. Thus, there is no sedimentation of powder in a corner where the plating solution is likely to stagnate. Furthermore, the plating-solution tank 35 can be made compact.

In both the embodiment shown in FIGS. 11 and 12 and the embodiment shown in FIG. 13, the time it takes for the plating solution to pass through the detour passage 93 can be increased by increasing the number of baffle plates 88. In the case of the embodiment shown in FIG. 14 in which no baffle plate is provided, the time it takes for the plating solution to pass through the detour passage 93 can be increased by increasing the length of the detour passage 93 as well.

FIG. 15 is a diagram (SEM diagram) showing results of an experiment which was conducted to examine an influence of the number of baffle plates on dissolution of copper oxide powder under a room-temperature condition. In this experiment, a solution to which copper oxide powder had been added was passed through the detour passage 93 in which zero, one, two, or three baffle plates were provided. After the passage of the solution, sediment of copper oxide powder on the bottom of the detour passage 93 was collected and microphotographed. FIG. 15 shows SEM images at magnifications of 50 times, 100 times, and 150 times.

In view of a friction loss in the plating-solution supply pipe 36 and a loss by a valve, a meter, a pipe joint, etc., the flow velocity of the plating solution flowing in the plating-solution tank 35 needs to be high to a certain degree in order to increase the copper ion concentration in the plating solution in the plating tanks 2. On the other hand, if the flow velocity of the plating solution is too high, the copper oxide powder may not be completely dissolved in the plating solution.

As can be seen from the experimental results shown in FIG. 15, almost no copper oxide powder remained in the detour passage 93 in the case of three baffle plates, whereas some copper oxide powder remained in the detour passage 93 in the case of zero baffle plate. These results show that the dissolution of copper oxide film is improved as the number of baffle plates increases. The time it takes for the plating solution to pass through the detour passage 93 was about 4 seconds in the case of zero baffle plate, about 8 seconds in the case of one baffle plate, about 12 seconds in the case of two baffle plates, and about 16 seconds in the case of three baffle plates.

These experimental results indicate that the time required for the plating solution to pass through the detour passage 93 should be more than 10 seconds corresponding to the use of one-and-a-half baffle plates, preferably more than about 12 seconds corresponding to the use of two baffle plates, and more preferably more than 16 seconds corresponding to the use of three baffle plates.

While the influence of the number of baffle plates on the dissolution of copper oxide powder has been described, an approach to promote the dissolution of copper oxide powder is not limited to the adjustment of the number of baffle plates. For example, it is possible to install a heater in the plating-solution tank 35, e.g. in the agitation tank 91, to promote the dissolution of copper oxide powder in the plating solution. However, if the plating solution is heated to a too high temperature, then coexisting components, such as additives, in the plating solution can be decomposed and deactivated. From this viewpoint, it is preferred to set an upper limit of the temperature of the plating solution in the agitation tank 91 to be not more than 50 C° so as not to cause decomposition of the additive(s). In the case of installing such a heater for heating the plating solution, only one baffle plate may be installed in the detour passage 93 so that it takes at least about 8 seconds for the plating solution to pass through the detour passage 93, or no baffle plate may be installed in the plating-solution tank 35. The heater installed in the agitation tank 91 makes it possible to fully dissolve the copper oxide powder in the plating solution when the plating solution is merely passing through the plating-solution tank 35.

A plating system according to a second embodiment will now be described with reference to FIG. 16. The plating system according to the second embodiment differs from the plating system according to the first embodiment in that the four plating tanks 2 are coupled in series. More specifically, the outer tank 6 and the inner tank 5 of each plating tank 2 are coupled to the inner tank 5 and the outer tank 6 of the adjacent plating tank 2 by a first connection pipe 110 and a second connection pipe 112, respectively. The first connection pipes 110 and the second connection pipes 112 are provided with pumps 113, respectively, for delivering the plating solution.

The plating-solution supply pipe 36 is coupled to the inner tank 5 of one of the four plating tanks 2, and the plating-solution return pipe 37 is coupled to the outer tank 6 of another one of the four plating tanks 2. The plating-solution supply pipe 36 is provided with a flow meter 38 and a flow control valve 39, and the plating-solution return pipe 37 is provided with a flow meter 115 and a plating-solution discharge valve 116. A concentration measuring device 118 for measuring the copper ion concentration in the plating solution is coupled to the outer tank 6 to which the plating-solution return pipe 37 is coupled. The same reference numerals are used for the same elements in the first embodiment, and duplicate descriptions thereof are omitted.

The plating system according to the second embodiment automatically measures the copper ion concentration in the plating solution while keeping the copper ion concentration in the plating solution substantially equal among the plating tanks 2. When it is necessary to replenish the plating solution with copper, the plating solution is delivered from the plating apparatus 1 to the plating-solution supply apparatus 20, while the plating solution containing copper in a relatively high concentration is supplied from the plating-solution supply apparatus 20 in the downstairs room to the plating apparatus 1.

A control sequence for adding copper oxide powder to the plating solution in the plating system according to the first embodiment will be described with reference to FIG. 17, and a control sequence for adding copper oxide powder to the plating solution in the plating system according to the second embodiment will be described with reference to FIG. 18. In the plating system according to the first embodiment, as shown in FIG. 17, in step 1, when the copper ion concentration in the plating solution has become lower than a set value, the plating controller 17 sends the signal indicating the replenishment demand value to the operation controller 32. In step 2, upon receipt of the signal, the operation controller 32 instructs the motor 31 to operate until the amount of copper oxide powder added to the plating solution reaches the replenishment demand value, so that the feeder 30 adds the copper oxide powder to the plating solution in the plating-solution tank 35 by the amount corresponding to the replenishment demand value.

In step 3, the operation controller 32 activates the agitation device 85, which agitates the plating solution to which the copper oxide powder has been added. The operation controller 32 stops the agitating operation of the agitation device 85 when a preset time has elapsed. In step 4, the plating solution to which the copper oxide powder has been added flows through the overflow tank 92 and the detour passage 93, while the copper oxide powder is dissolved in the plating solution. In step 5, the plating solution in which the copper oxide powder has been dissolved is supplied to the plating tanks 2 of the plating apparatus 1 through the plating-solution supply pipe 36. In this manner, the copper ion concentration in the plating solution used in the plating apparatus 1 is maintained at a set value. According to this embodiment, a necessary amount of copper oxide powder can be automatically added to and dissolved in the plating solution, and a predetermined amount of the plating solution can be supplied to each plating tank 2. Therefore, the copper ion concentration in the plating solution in each plating tank 2 can be regulated and maintained at a predetermined value without decreasing the throughput of the plating apparatus 1.

In the plating system according to the second embodiment, copper oxide powder is added to the plating solution in the following manner. The copper ion concentration in the plating solution held in the plating tanks 2 is continually measured by the concentration measuring device 118, and the measured value of the copper ion concentration is monitored by the plating controller 17. As shown in FIG. 18, in step 1, when the copper ion concentration in the plating solution in the plating tanks 2 has become lower than a set value, the plating controller 17 sends the signal indicating the replenishment demand value to the operation controller 32 of the plating-solution supply apparatus 20. In step 2, the plating-solution discharge valve 116 for discharging the plating solution from the plating tanks 2 is opened to deliver the plating solution from the plating tanks 2 to the plating-solution tank 35. This plating-solution discharge valve 116 is kept open for a predetermined period of time so that the plating solution is delivered in an amount of not more than the maximum volume of the plating-solution tank 35.

In step 3, upon receipt of the above signal, the operation controller 32 instructs the motor 31 to operate until the amount of copper oxide powder added to the plating solution reaches the replenishment demand value, so that the feeder 30 adds the copper oxide powder, in an amount corresponding to the replenishment demand value, to the plating solution in the plating-solution tank 35. Step 2 and step 3 may be performed simultaneously, or step 3 may be performed prior to step 2. In step 4, the operation controller 32 activates the agitation device 85, which agitates the plating solution to which the copper oxide powder has been added. The operation controller 32 stops the agitating operation of the agitation device 85 when a preset time has elapsed.

In step 5, the plating solution to which the copper oxide powder has been added flows through the overflow tank 92 and the detour passage 93, while the copper oxide powder is dissolved in the plating solution. In step 6, the plating solution in which the copper oxide powder has been dissolved is supplied to one of the plating tanks 2 of the plating apparatus 1 through the plating-solution supply pipe 36. The plating tanks 2 communicate with each other through the first connection pipes 110 and the second connection pipes 112, and the plating solution circulates through all of the plating tanks 2 by the operations of the pumps 113 attached to the first connection pipes 110 and the second connection pipes 112 that couple the plating tanks 2 to each other. In this manner, the copper ion concentration in the plating solution used in the plating apparatus 1 is maintained at a set value.

As shown in FIG. 1, in the plating system according to the first embodiment, the plating-solution supply pipe 36 has the branch pipes 36 a coupled to the plating tanks 2, respectively, and the plating solutions having the same concentration are supplied to the plating tanks 2. In the plating system according to the second embodiment, the plating tanks 2 communicate with each other and the plating-solution supply pipe 36 is coupled to one of the plating tanks 2. Therefore, in both of these embodiments, the concentration of the plating solution in the plating tanks 2 can be kept uniform. According to these embodiments, a quality of a copper film formed by plating can be improved and, in addition, a variation in the results of plating among the plating tanks 2 can be prevented.

The average particle size of copper oxide powder (as measured by a laser diffraction/scattering method) is preferably in the range of 10 micrometers to 200 micrometers, more preferably in the range of 20 micrometers to 100 micrometers. If the average particle size is too small, copper oxide powder can scatter in the air during the supply of the powder. If the average particle size is too large, the powder may not be quickly dissolved in the solution.

A plating method capable of forming a higher-quality copper film on a substrate can be provided by using a plating solution to which pelletized solid materials comprising metal copper have been added. The use of such pelletized solid materials comprising metal copper allows copper powder containing few impurities to coexist with copper oxide powder, leading to an enhanced plating film quality. Further, the use of such pellets can more effectively prevent scattering of powder upon the supply of the powder.

While an alkali metal in a powder form is generally at risk for firing or explosion, powder of metal copper is at low risk for firing or explosion. Powder of metal copper can therefore be shaped into pellets. As described above e.g. with reference to FIG. 1, instead of or together with copper oxide powder, such pelletized solid materials comprising metal copper can be supplied to the plating-solution tank 35. It is also possible to use pellets of metal copper together with pellets of copper oxide.

If the pelletized solid materials are too hard, such materials can cause a trouble in the plating-solution supply apparatus 20. If the pelletized solid materials are too soft, it is possible that scattering of powder may not be effectively prevented. Thus, it is preferred to use pellets having an appropriate hardness.

While the pelletized solid materials have been described, it is also possible for copper plating to use small-diameter solid copper balls or a strip-shaped material, obtained by shaping solid copper into a ribbon-like or tape-like shape. In that case, a shaft of the feeder 30 may have a function of crushing such solid materials.

While the powder container, the plating-solution supply apparatus, etc. have been described with reference to the case of plating a substrate with copper, the powder container, the plating system and the plating method described above can be used also in a case of plating a substrate with other metal such as indium.

The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims. 

What is claimed is:
 1. An apparatus for supplying a plating solution, in which powder comprising at least a metal to be used in plating has been dissolved, to a plating tank, comprising: a hopper having an inlet which is connectable to a powder conduit of a powder container holding the powder therein; a feeder which communicates with a bottom opening of the hopper; a motor coupled to the feeder; and a plating-solution tank coupled to an outlet of the feeder and configured to dissolve the powder in the plating solution.
 2. The apparatus according to claim 1, further comprising: a weight measuring device configured to measure a weight of the hopper and the feeder; and an operation controller configured to control an operation of the motor based on a change in a measured value of the weight.
 3. The apparatus according to claim 2, wherein the operation controller is configured to calculate an amount of the powder added to the plating solution from a change in the measured value of the weight, and instruct the motor to operate until the amount of the added powder reaches a target value.
 4. The apparatus according to claim 1, wherein the inlet of the hopper has a connecting seal whose inner diameter gradually decreases with a distance from a distal end of the inlet.
 5. The apparatus according to claim 4, wherein the connecting seal is composed of an elastic material.
 6. The apparatus according to claim 1, further comprising: an airtight chamber in which the inlet of the hopper is located, the airtight chamber including a door which allows the powder container to be carried into the airtight chamber, and a glove which constitutes part of a wall of the airtight chamber.
 7. The apparatus according to claim 6, wherein the airtight chamber further includes an exhaust port for connecting an interior space to a negative-pressure source.
 8. The apparatus according to claim 6, wherein a vibrating device capable of vibrating the powder container is disposed in the airtight chamber.
 9. The apparatus according to claim 6, wherein a vacuum clamp capable of holding the powder container is disposed in the airtight chamber.
 10. The apparatus according to claim 1, wherein the plating-solution tank includes an agitation device for agitating the plating solution.
 11. The apparatus according to claim 10, wherein the plating-solution tank includes an agitation tank in which the agitation device is disposed, and an overflow tank coupled to a through-hole formed in a lower portion of the agitation tank.
 12. The apparatus according to claim 11, wherein the plating-solution tank further includes a detour passage located adjacent to the overflow tank.
 13. The apparatus according to claim 11, wherein the plating-solution tank further includes a plurality of baffle plates disposed in the overflow tank, the plurality of baffle plates being staggered.
 14. The apparatus according to claim 1, further comprising: an enclosure cover that surrounds connection portions of the feeder and the plating-solution tank; and an inert-gas supply line which communicates with an interior of the enclosure cover.
 15. A plating system comprising: a plurality of plating tanks each for plating a substrate; a plating-solution supply apparatus including (i) a hopper having an inlet which is connectable to a powder conduit of a powder container holding therein powder comprising at least a metal to be used in plating of the substrate, (ii) a feeder which communicates with a bottom opening of the hopper, (iv) a motor coupled to the feeder, and (v) a plating-solution tank coupled to an outlet of the feeder and configured to dissolve the powder in a plating solution; and a plating-solution supply pipe extending from the plating-solution supply apparatus to the plating tanks.
 16. The plating system according to claim 15, further comprising: a plating-solution return pipe extending from the plating tanks to the plating-solution supply apparatus.
 17. A method of supplying powder, comprising at least a metal to be used in plating, to a plating solution, comprising: coupling a powder conduit of a powder container, holding the powder therein, to an inlet of a hopper; supplying the powder from the powder container to the hopper; operating a feeder which communicates with a bottom opening of the hopper while measuring a weight of the feeder and the hopper in which the powder is stored; and adding the powder to the plating solution by the feeder based on a change in a measured value of the weight.
 18. The method according to claim 17, further comprising: agitating the plating solution to which the powder has been added.
 19. The method according to claim 17, further comprising: calculating an amount of the powder added to the plating solution from a change in the measured value of the weight; and operating the feeder until the amount of the added powder reaches a target value.
 20. A powder container for holding powder comprising at least a metal to be used in plating, comprising: a container body capable of holding the powder therein; a powder conduit coupled to the container body; and a valve attached to the powder conduit.
 21. The powder container according to claim 20, wherein a distal end of the powder conduit has a shape of a truncated cone.
 22. A method of plating a substrate, comprising: delivering a plating solution from a plating tank to a plating-solution tank; calculating an amount of powder to be added to the plating solution held in the plating-solution tank based on a metal ion concentration in the plating solution in the plating tank, the powder comprising at least a metal to be used in plating; supplying the powder to the plating solution held in the plating-solution tank; dissolving the powder in the plating solution held in the plating-solution tank; supplying the plating solution, in which the powder has been dissolved, from the plating-solution tank to the plating tank; bringing a substrate into contact with the plating solution held in the plating tank; and causing an electrochemical reaction in the plating solution held in the plating tank to deposit the metal on a surface of the substrate.
 23. The method according to claim 22, wherein the plating tank comprises a plurality of plating tanks, and wherein the plating solution is supplied from the plating-solution tank to each of the plating tanks while controlling a flow rate of the plating solution.
 24. The method according to claim 22, wherein: the plating tank comprises a plurality of plating tanks, and a metal ion concentration in the plating solution in the plurality of plating tanks is continually monitored; and when the metal ion concentration has become lower than a predetermined value, the plating solution in the plating tanks is delivered to the plating-solution tank, while the plating solution in the plating-solution tank is supplied to one of the plurality of plating tanks.
 25. A non-transitory computer-readable storage medium that stores a computer program for performing a method of electroplating a substrate, the method comprising: delivering a plating solution from a plating tank to a plating-solution tank; supplying powder to the plating solution held in the plating-solution tank, the powder comprising at least a metal to be used in plating; dissolving the powder in the plating solution held in the plating-solution tank; supplying the plating solution, in which the powder has been dissolved, from the plating-solution tank to the plating tank; bringing a substrate into contact with the plating solution held in the plating tank; and causing an electrochemical reaction in the plating solution held in the plating tank to deposit the metal on a surface of the substrate.
 26. A non-transitory computer-readable storage medium that stores a computer program for performing a method of electroplating a substrate, the method comprising: monitoring whether a concentration of metal ions contained in a plating solution in a plating tank is lower than a predetermined value; calculating an amount of powder to be added to the plating solution when the concentration of metal ions is lower than the predetermined value, the powder comprising at least a metal; delivering the plating solution from the plating tank to a plating-solution tank; supplying the powder to the plating solution held in the plating-solution tank until an amount of the added powder reaches the calculated amount; dissolving the powder in the plating solution held in the plating-solution tank; supplying the plating solution, in which the powder has been dissolved, from the plating-solution tank to the plating tank; bringing a substrate into contact with the plating solution held in the plating tank; and causing an electrochemical reaction in the plating solution held in the plating tank to deposit the metal on a surface of the substrate. 